JPS6217765Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical multiplexer (optical star coupler) having a function of uniformly distributing an input optical signal to a large number of output terminals at the same time.

Optical multiplexers are also called optical star couplers, and are used in optical data bus systems in which communication between a large number of terminals can be performed simultaneously, and in distributing optical signals among an unspecified number of subscriber terminals.

Optical multi-branchers include a distributed coupling type that utilizes coupling between radiation modes by thermally fusing a large number of optical fibers;
It is broadly divided into a mixing element type that multiple-reflects light at a mixing part and then distributes it to an output optical fiber. The latter optical multi-brancher is suitable for cases where a large number of branches such as 8 or 16 branches are required because the number of branches can be expanded relatively easily.

FIG. 1 is a perspective view showing an example of this mixing element type optical splitter. The input light from the plurality of input fibers 1 is reflected many times by the rectangular parallelepiped-shaped mixing element 3 surrounded by total reflection surfaces, and after the power distribution in the width direction becomes uniform, the light is transmitted from the plurality of output optical fibers 2. The output is distributed to fiber arrays.

In an optical multiplexer, it is important that variations in distributed power be small between output terminals (fibers). For this purpose, it is necessary that the input light be reflected as many times as possible in the width W direction.

That is, the ratio L/W between the length L and the width W of the mixing portion 3 becomes an important parameter for the variation in distributed power. According to experiments, in order to suppress the distribution power variation to 1 dB or less, L/W should be 50 to 100.
I found out that I needed to set it to . Therefore, to achieve 10 branches using a fiber with a core diameter of 100 μm and a cladding diameter of 150 μm, the width is 1.5 mm,
A mixing section with a light guide layer 0.1 mm thick and 75-100 mm long is required.

As described above, it is very difficult to form guide layers having extremely different thicknesses, widths, and lengths with low loss. In addition, the length of the optical branch itself is approximately 150 mm.
The size is ~200mm, which poses problems in terms of mounting. Further, unless the coefficient of thermal expansion of the mixing portion is matched with that of the portion holding the mixing portion, distortion will increase and there will be drawbacks such as failure to obtain good loss-temperature characteristics.

An object of the present invention is to provide an optical multiplexer that eliminates the above-mentioned drawbacks.

The branching device of the present invention includes an input optical fiber array consisting of a plurality of optical fibers arranged in a plane, and an input optical fiber array arranged so that the optical axis plane coincides with the plane and converts the input light from the input fiber array into parallel light. 1; a polygonal columnar mixing glass block in which predetermined portions of an upper surface, a lower surface, and at least one side surface totally reflect light and mix optical power by inputting the parallel light; an output optical fiber array consisting of a second cylindrical lens that focuses mixed parallel light emitted from the glass block and a plurality of optical fibers arranged to coincide with the optical axis plane of the second cylindrical lens; It is composed of.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a perspective view showing the first embodiment of the present invention.

This embodiment has an input fiber array 10 made up of a plurality of optical fibers arranged on a plane, and an optical axis plane that coincides with the plane, and has a function of converting input light from the fiber array 1 into parallel light only in the Y direction. a cylindrical lens 4; a triangular prism glass block 30 whose upper and lower surfaces (front and rear surfaces in FIG. 2) are surfaces perpendicular to the optical axis plane of the cylindrical lens;
It consists of a cylindrical lens 5 for linearly imaging the light passing through the glass block 30, and an output fiber array 20 consisting of a plurality of optical fibers arranged at the imaging position of the cylindrical lens 5. Here, the widths of the cylindrical lens 5, the glass block 30, and the fiber row 20 are equal. The upper and lower surfaces of the glass block 30 and the side surfaces of the cylindrical lenses 4 and 5 are mirror-polished and serve as surfaces for total reflection of light. The input light is repeatedly reflected on these surfaces, so that the power distribution in the X direction becomes uniform. Surfaces 6 and 7 of the glass block are total reflection surfaces for folding back the light beam.

In this embodiment, the cylindrical lenses 4 and 5 are used as collimating lenses in the Y direction to prevent the light beam from diffusing in the Y direction, and the upper and lower surfaces of the glass block 30a are used as total reflection surfaces to prevent the light beam from entering the glass block. A sufficient mixing length (corresponding to L in FIG. 1) can be obtained by mixing the optical power by confining the light beam into the light beam, and by folding the light beam by the reflecting surfaces 6 and 7.

FIG. 3 is a perspective view showing a second embodiment of the present invention, in which a glass block 31 is formed of a pentagonal prism.

FIG. 4 is a perspective view showing a third embodiment of the present invention, which is constructed so that the light beam is reflected many times on two opposing reflecting surfaces 6 and 7 of a glass block 31 formed of a square prism. be.

As in the conventional example, when achieving 10 branches using a fiber with a core diameter of 100 μm and a clad outer diameter of 150 μm, the first embodiment uses a fiber with a thickness of 1.5 mm and a base of 75 mm.
A 100mm right-angled isosceles triangle may be used. However, as a matter of course, there is no need for a portion through which the light beam does not pass, and it is sufficient that the surface through which the light passes forms a right-angled isosceles triangle. Further, in the third embodiment, when the reflection is made twice on each opposing surface, a square prism with a thickness of 1.5 mm, a width of 15 to 20 mm, and a length of about 10 mm may be used.

As described above, the present invention allows the mixing part to be made smaller even with a large number of branches, and further reduces the loss due to the difference in thermal expansion coefficient between the mixing part (glass) and the mixing part holding part (metal) by reducing the size. −
This has the effect of significantly improving temperature characteristics. Further, since the ratio of thickness, width and length of the glass block which is the mixing part is small, the mixing part can be easily processed and cost reduction can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a conventional optical multiplexer, and FIGS. 2, 3, and 4 are perspective views showing first, second, and third embodiments of the present invention, respectively. In the figure, 1... Input fiber, 2... Output fiber, 3, 30, 31, 32... Mixing element, 4, 5... Cylindrical lens, 6, 7
... Mirror surface, 10 ... Input fiber row, 20 ...
...Output fiber row.

Claims (1)

[Scope of utility model registration request] an input optical fiber array consisting of a plurality of optical fibers arranged in a plane; a first cylindrical lens arranged such that its optical axis plane coincides with the plane and converts input light from the input optical fiber array into parallel light; A polygonal columnar mixing glass block in which predetermined portions of an upper surface, a lower surface, and at least one side surface totally reflect light and mix the optical power by inputting the parallel light; and a mixing glass block emitted from the glass block. and an output optical fiber array consisting of a plurality of optical fibers arranged to coincide with the optical axis plane of the second cylindrical lens, and the polygonal columnar mixing The optical multiplexer is characterized in that the glass block multiple-reflects the light in the direction of the optical axis of the cylindrical lens, and also multiple-reflects the light in the direction in which the light travels, thereby performing mode mixing.